https://github.com/koterpillar/appendmap

A Data.Map wrapper with a Monoid instance that delegates to the individual keys
https://github.com/koterpillar/appendmap

containers data-structures haskell map monoid semigroup

Last synced: 7 days ago
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A Data.Map wrapper with a Monoid instance that delegates to the individual keys

• Host: GitHub
• URL: https://github.com/koterpillar/appendmap
• Owner: koterpillar
• License: bsd-3-clause
• Created: 2018-08-16T10:33:40.000Z (about 6 years ago)
• Default Branch: master
• Last Pushed: 2024-02-17T11:10:46.000Z (9 months ago)
• Last Synced: 2024-04-26T01:02:04.363Z (7 months ago)
• Topics: containers, data-structures, haskell, map, monoid, semigroup
• Language: Haskell
• Size: 23.4 KB
• Stars: 2
• Watchers: 2
• Forks: 0
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • Changelog: ChangeLog.md
  • License: LICENSE

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README

        
# appendmap

![Build status](https://github.com/koterpillar/appendmap/workflows/Build/badge.svg)

[![Hackage](https://img.shields.io/hackage/v/appendmap.svg)](https://hackage.haskell.org/package/appendmap)

[![Stackage LTS](https://www.stackage.org/package/appendmap/badge/lts)](https://www.stackage.org/lts/package/appendmap)

[![Hackage dependencies](https://img.shields.io/hackage-deps/v/appendmap.svg)](https://packdeps.haskellers.com/feed?needle=appendmap)

A `Data.Map` wrapper with a `Semigroup` and `Monoid` instances that delegate to

the individual keys.

```haskell

import qualified Data.Map as Map

import Data.Map.Append

> one = AppendMap $ Map.fromList [(1, "hello"), (2, "goodbye")]

> two = AppendMap $ Map.fromList [(1, "world"), (3, "again")]

> unAppendMap (one <> two)

fromList [(1, "helloworld"), (2, "goodbye"), (3, "again")]

```

## Motivation

`Data.Map` has a `Semigroup` instance that keeps the values from the first

argument in case of a key conflict:

```haskell

import qualified Data.Map as Map

import Data.Map.Append

> Map.fromList [(1, "hello")] <> Map.fromList [(1, "goodbye")]

fromList [(1, "hello")]

```

A different instance has been suggested for a long time

([1](https://mail.haskell.org/pipermail/libraries/2012-April/017743.html),

[2](https://ghc.haskell.org/trac/ghc/ticket/1460)), but this is a breaking change and hasn't happened yet (as of 2018-08).

## Development

Source code is formatted with `hindent` _then_ `stylish-haskell`.

### Releasing

* Run `./bumpversion patch|minor|major`. This will create a new version and push

  it to the repository to be released.